Ca Channel blockers

Question 1

Mechanism of action?

Answer 1

They decrease Ca entry into vascular &cardiac cells.

• This causes relaxation &vasoldiation in the arterial smooth muscle, lowering arterial pressure.
• In the heart, they reduce myocardial contractility, they suppress cardiac conduction, particularly across the AV node; slowing the ventricular rate. Reduced cardiac rate, contractility &afterload decreases the myocardial oxygen demand which prevents angina.

Question 2

Angina?

Answer 2

Angina pectoris is a type of chest pain caused by reduced blood flow to the heart. It is a symptom of coronary artery disease, often described as squeezing, pressure, heaviness, tightness or pain in the chest.

Question 3

What are the two classes of Ca channel blockers?

Answer 3

• Dihydropyridines : relatively selective for the vasculate.

* Non-dihyrdopyridines : mostly selective for the heart

Question 4

Dihydropyridines drugs?

Answer 4

Amlodipine, Nifedipine (ADALATE), Barnidipine, Clevidipine, Felodipine (FLODIL), Isradipine, Lacidipine, Lercanidipine (ZANIDIP), Manidipine, Nicardipine (LOXEN), Nisolidipine, Nitrendipine (BAYPRESS).

Living room : Isra is a Clever Fellow, Barni &Mani on the sofas. Lercani on the window, tables : Nitren &Nisoli. Laci on the carpet. Nicar LOXEN on the chair relaxing. Nife &Amlo are famous needless to assign them to loci.

Question 5

Non-dihydropyridines drugs?

Answer 5

Verapamil, the most cardioselective.

Diltiazem; has some effect on the vessels.

Question 6

Indications?

Answer 6

• Amlodipine, and to a lesser extent, Nifedipine are used as first/second line treatment for hypertension to reduce risk of stroke, myocardial infarction &death from cardiovascular diseases.
• all Ca channel blockers are used to control symptoms of stable angina.
• non-dihydropyridines are used to control cardiac rate in supraventricular arrhythmias : AF, atrial flutter and SVT.

Question 7

Important AE?

Answer 7

• dihydropiridines : ankle swelling, flushing, headache, palpitations : caused by vasodilation &the compensatory tachycardia.
• non-dihydropyridines : Verapamil : constipation &less often, but more seriously : bradycardia, heart block &cardiac failure. while Diltiazem can cause both vasodilation issued problems &heart related side effects.

Question 8

Why should Dihydropyridines be avoided in unstable angina ?

Answer 8

Vasodilation induces a reflex increase in contractility (compensatory tachycardia) which can offput &increase myocardial oxygen demand.

Question 9

Why should Non-dihydropyridines not be used in combination with beta blockers (except under specialist supervision)?

Answer 9

both are negatively inotropic &chronotropic : bradycardia, heart failure &asystole (cardiac arrest rhythm, the heart isn’t functioning)

Question 10

Plasma half-life of Amlodipine?

Answer 10

35-50 hours (the longest amongst Ca channel blockers)

All Ca channel blockers (&ACE) are advised to take the morning.

If you have many antihypertensive drugs, take some the morning, some the evening at bedtime.

Question 11

Plasma half-life of Nifedipine?

Answer 11

2-3 hours

Question 12

Plasma half-life of Verapamil?

Answer 12

2-8 hours

Question 13

Plasma half-life of Diltiazem?

Answer 13

6-8 hours